[meteorite-list] NASA's Near-Earth Object Report to Congress

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 12 Mar 2007 12:35:13 -0700 (PDT)
Message-ID: <200703121935.l2CJZDo27080_at_zagami.jpl.nasa.gov>

http://neo.jpl.nasa.gov/neo/report2007.html

Near-Earth Object
Survey and Defintion
Analysis of Alternvatives

Report to Congress
March 2007

Note: The full report is available here (PDF - 790K):

http://www.nasa.gov/pdf/171331main_NEO_report_march07.pdf

SUMMARY

Section 321 of the NASA Authorization Act of 2005 (Public Law No.
109-155), also known as the George E. Brown, Jr. Near-Earth Object
Survey Act, directs the NASA Administrator to transmit an initial report
to Congress not later than one year after the date of enactment that
provides: (1) an analysis of possible alternatives that NASA may employ
to carry out the survey program of near-Earth Objects (NEO), including
ground- based and space-based alternatives with technical descriptions;
(2) a recommended option and proposed budget to carry out the survey
program pursuant to the recommended option; and (3) an analysis of
possible alternatives that NASA could employ to divert an object on a
likely collision course with Earth.

The objectives of the George E. Brown, Jr. NEO Survey Program are to
detect, track, catalogue, and characterize the physical characteristics
of NEOs equal to or larger than 140 meters in diameter with a perihelion
distance of less than 1.3 AU (Astronomical Units) from the Sun,
achieving 90 percent completion of the survey within 15 years after
enactment of the NASA Authorization Act of 2005. The Act was signed into
law by President Bush on December 30, 2005.

A study team, led by NASA's Office of Program Analysis and Evaluation
(PA&E), conducted the analysis of alternatives with inputs from several
other U.S. government agencies, international organizations, and
representatives of private organizations. The team developed a range of
possible options from public and private sources and then analyzed their
capabilities and levels of performance including development schedules
and technical risks.

Key Findings for the Survey Program:

    * The goal of the Survey Program should be modified to detect,
      track, catalogue, and characterize, by the end of 2020, 90 percent
      of all Potentially Hazardous Objects (PHOs) greater than 140
      meters whose orbits pass within 0.05 AU of the Earth's orbit (as
      opposed to surveying for all NEOs).

    * The Agency could achieve the specified goal of surveying for 90
      percent of the potentially hazardous NEOs by the end of 2020 by
      partnering with other government agencies on potential future
      optical ground-based observatories and building a dedicated NEO
      survey asset assuming the partners' potential ground assets come
      online by 2010 and 2014, and a dedicated asset by 2015.

    * Together, the two observatories potentially to be developed by
      other government agencies could complete 83 percent of the survey
      by 2020 if observing time at these observatories is shared with
      NASA's NEO Survey Program.

    * New space-based infrared systems, combined with shared
      ground-based assets, could reduce the overall time to reach the 90
      percent goal by at least three years. Space systems have
      additional benefits as well as costs and risks compared to
      ground-based alternatives.

    * Radar systems cannot contribute to the search for potentially
      hazardous objects, but may be used to rapidly refine tracking and
      to determine object sizes for a few NEOs of potentially high
      interest. Existing radar systems are currently oversubscribed by
      other missions.

    * Determining a NEO's mass and orbit is required to determine
      whether it represents a potential threat and to provide required
      information for most alternatives to mitigate such a threat.
      Beyond these parameters, characterization requirements and
      capabilities are tied directly to the mitigation strategy selected.

Key Findings for Diverting a Potentially Hazardous Object (PHO):

The study team assessed a series of approaches that could be used to
divert a NEO potentially on a collision course with Earth. Nuclear
explosives, as well as non-nuclear options, were assessed.

    * Nuclear standoff explosions are assessed to be 10-100 times more
      effective than the non-nuclear alternatives analyzed in this
      study. Other techniques involving the surface or subsurface use of
      nuclear explosives may be more efficient, but they run an
      increased risk of fracturing the target NEO. They also carry
      higher development and operations risks.

    * Non-nuclear kinetic impactors are the most mature approach and
      could be used in some deflection/mitigation scenarios, especially
      for NEOs that consist of a single small, solid body.

    * "Slow push" mitigation techniques are the most expensive, have the
      lowest level of technical readiness, and their ability to both
      travel to and divert a threatening NEO would be limited unless
      mission durations of many years to decades are possible.

    * 30-80 percent of potentially hazardous NEOs are in orbits that are
      beyond the capability of current or planned launch systems.
      Therefore, planetary gravity assist swingby trajectories or
      on-orbit assembly of modular propulsion systems may be needed to
      augment launch vehicle performance, if these objects need to be
      deflected.

Alternatives Considered to Detect, Track, Characterize, and
Deflect/Mitigate NEOs

The following tables provide a summary of the options considered.
Technical descriptions of each option, as well as other combinations of
alternatives, can be found in subsequent sections of this report. For
each option, Table 1 shows the percentage of PHOs that would be found by
the survey by the end of 2020 and the year each option would achieve 90
percent completion, starting with the option of sharing the use of
potential ground-based observatories, which will be referred to as the
"Reference" architecture through the rest of this document. Details
regarding the availability of assets for each option are also found in
subsequent sections. Table 1 shows that individually each of the first
three options fall short of meeting the Congressional goal. As shown in
the last line of Table 1, the minimum survey architecture that achieves
the goal would be a combination of the shared ground-based assets plus
one of two dedicated asset options.

Table 1. Detection and Tracking Capability Options & Summary Results

Table 2. Characterization Options

Table 3. Impulsive Deflection/Mitigation Options

Table 4. Slow Push Deflection/Mitigation Options

Recommended Survey Program

Currently, NASA carries out the "Spaceguard Survey" to find NEOs greater
than 1 kilometer in diameter, and this program is currently budgeted at
$4.1 million per year for FY 2006 through FY 2012. We also have
benefited from knowledge gained in our Discovery space mission series,
such as the Near Earth Asteroid Rendezvous (NEAR), Deep Impact, and
Stardust missions that have expanded our knowledge of near-Earth
asteroids and comets. Participation by NASA in international
collaborations such as Japan's Hayabusa mission to the NEO "Itokawa"
also greatly benefited our understanding of these objects. NASA's Dawn
mission, expected to launch in June 2007, will increase our
understanding of the two largest known main belt asteroids, Ceres and
Vesta, between the planets Mars and Jupiter. NASA conducts survey
programs on many celestial objects - the existing Spaceguard program for
NEOs, surveys for Kuiper Belt Objects, the search for extra-solar
planets, and other objects of interest such as black holes to understand
the origins of our universe. Our Discovery mission series in planetary
science may offer additional opportunities in the future beyond our
current survey efforts.

NASA recommends that the program continue as currently planned, and we
will also take advantage of opportunities using potential dual-use
telescopes and spacecraft - and partner with other agencies as feasible
- to attempt to achieve the legislated goal within 15 years. However,
due to current budget constraints, NASA cannot initiate a new program at
this time.
Received on Mon 12 Mar 2007 03:35:13 PM PDT